Precipitation reactions solids

Analytical Chemistry Bonding and Structure in Solids Crystallography Lasers, Solid-State Microscopy (Chemistry) Phase Transformations, Crystallographic Aspect Precipitation Reactions Solid-State Imaging Devices Superconductors, High ItMPERATURE Surface Chemistry... 

Solid Compounds. The tripositive actinide ions resemble tripositive lanthanide ions in their precipitation reactions (13,14,17,20,22). Tetrapositive actinide ions are similar in this respect to Ce . Thus the duorides and oxalates are insoluble in acid solution, and the nitrates, sulfates, perchlorates, and sulfides are all soluble. The tetrapositive actinide ions form insoluble iodates and various substituted arsenates even in rather strongly acid solution. The MO2 actinide ions can be precipitated as the potassium salt from strong carbonate solutions. In solutions containing a high concentration of sodium and acetate ions, the actinide ions form the insoluble crystalline salt NaM02(02CCH2)3. The hydroxides of all four ionic types are insoluble ... 

Precipitation reactions, like all reactions, reach a position of equilibrium. Suppose, for example, solutions of Sr(N03)2 and K2Cr04 are mixed. In this case, Sr2+ ions combine with Cr042- ions to form a yellow precipitate of strontium chromate, SrCr04 (Figure 16.1). Very quickly, an equilibrium is established between the solid and the corresponding ions in solution ... 

Precipitate A solid that forms when two solutions are mixed, 78 Precipitation diagram, 78 Precipitation reaction Formation of an insoluble solid when two electrolyte solutions are mixed, 78,95-96q diagram, 78... 

When we mix two solutions the result is often simply a new solution that contains both solutes. However, in some cases the solutes can react with each other. For instance, when we mix a colorless aqueous solution of silver nitrate with a clear yellow aqueous solution of potassium chromate, a red solid forms, indicating that a chemical reaction has occurred (Fig. 1.1). This section and the next two introduce three of the main types of chemical reactions precipitation reactions, acid-base reactions, and redox reactions, all of which are discussed in more depth in later chapters. (The fourth type of reaction discussed in this text, Lewis acid-base reactions, is introduced in Section 10.2.) Because many chemical reactions take place in solution, particularly in water, in this section we begin by considering the nature of aqueous solutions. 

In a precipitation reaction, an insoluble solid product forms when we mix two electrolyte solutions. When an insoluble substance is formed in water, it immediately precipitates. In the chemical equation for a precipitation reaction, we use (aq) to indicate substances that are dissolved in water and (s) to indicate the solid that has precipitated ... 

The net ionic equation shows that Ag+ ions combine with Cl ions to precipitate as solid silver chloride, AgCl (see Fig. 1.5). A net ionic equation focuses our attention on the change that results from the chemical reaction. 

In addition to effects on the concentration of anions, the redox potential can affect the oxidation state and solubility of the metal ion directly. The most important examples of this are the dissolution of iron and manganese under reducing conditions. The oxidized forms of these elements (Fe(III) and Mn(IV)) form very insoluble oxides and hydroxides, while the reduced forms (Fe(II) and Mn(II)) are orders of magnitude more soluble (in the absence of S( — II)). The oxidation or reduction of the metals, which can occur fairly rapidly at oxic-anoxic interfaces, has an important "domino" effect on the distribution of many other metals in the system due to the importance of iron and manganese oxides in adsorption reactions. In an interesting example of this, it has been suggested that arsenate accumulates in the upper, oxidized layers of some sediments by diffusion of As(III), Fe(II), and Mn(II) from the deeper, reduced zones. In the aerobic zone, the cations are oxidized by oxygen, and precipitate. The solids can then oxidize, as As(III) to As(V), which is subsequently immobilized by sorption onto other Fe or Mn oxyhydroxide particles (Takamatsu et al, 1985). 

The importance of one other type of reaction that metal ions undergo has been recognized and studied extensively in the past 40 years. This reaction is adsorption, in which metal ions bind to the surface of particulate matter and are thereby transported as part of a solid phase even though they do not form an identifiable precipitate. Conceptually, these reactions can be thought of as hybrids between complexation and precipitation reactions. Most studies of these reactions have used metal oxides or hydroxides as the solid (adsorbent) phase, and the... 

The diversity of chemical reactions is immense. To make sense of this vast expanse of chemistry, we need a system for grouping chemical reactions into categories. The reactions within each category should share some characteristics or follow a common theme. One relatively simple category is precipitation reactions, in which cations and anions in aqueous solution combine to form neutral insoluble solids. 

To understand precipitation reactions, it is essential to work with the ionic species that exist in aqueous solution. For instance, mixing colorless solutions of lead(II) nitrate and potassium iodide causes a brilliant yellow solid to precipitate from the mixture (Figure 4-4t. To identity this yellow solid, we must examine the chemical species present in the solutions. 

The simplest balanced chemical equation for a precipitation reaction is a net ionic equation that has ions as the reactants and a neutral solid as the product. In a precipitation reaction, reactant ions combine to form a neutral ionic solid. One reactant carries positive charge and the other carries negative charge, but the product is electrically neutral. Because electrical charge always is conserved, the total positive charge of the reacting cations... 

C04-0121. Lithopone, a brilliant white pigment used in paints, paper, and white rubber products, is a mixture of two insoluble Ionic solids, ZnS and BaSOq. Suggest how 1.0 kg of lithopone could be prepared by a precipitation reaction. 

C16-0026. Figure 16-12Z> shows the precipitation reaction to form AgBr. Calculate the amount of AgBr solid that forms and the concentrations of Ag and Br" ions remaining in solution if 0.500 L each of 1.00 M solutions of AgN03 and KBr are mixed together. 

Precipitate A solid that forms in a solution due to a chemical reaction taking place. 

Species with low solubility in water may exist in solid form (e.g., Ag2S, BaS()4) or liquid form (e.g., chlorinated solvents). Precipitation reactions and immiscible-phase separation are important processes affecting this type of speciation. 

The Ostwald Step Rule, or the rule of stages postulates that the precipitate with the highest solubility, i.e., the least stable solid phase will form first in a consecutive precipitation reaction. This rule is very well documented mineral formation via precursors and intermediates can be explained by the kinetics of the nucleation process. The precipitation sequence results because the nucleation of a more soluble... 

Redox cycling of iron in salt marsh sediments. The solid lines and the dashed lines indicate redox reactions and precipitation reactions, respectively. 

This book deals only with the chemistry of the mineral-water interface, and so at first glance, the book might appear to have a relatively narrow focus. However, the range of chemical and physical processes considered is actually quite broad, and the general and comprehensive nature of the topics makes this volume unique. The technical papers are organized into physical properties of the mineral-water interface adsorption ion exchange surface spectroscopy dissolution, precipitation, and solid solution formation and transformation reactions at the mineral-water interface. The introductory chapter presents an overview of recent research advances in each of these six areas and discusses important features of each technical paper. Several papers address the complex ways in which some processes are interrelated, for example, the effect of adsorption reactions on the catalysis of electron transfer reactions by mineral surfaces. 

It is necessary to consider a number of equilibrium reactions in an analysis of a hydrometallurgical process. These include complexing reactions that occur in solution as well as solubility reactions that define equilibria for the dissolution and precipitation of solid phases. As an example, in analyzing the precipitation of iron compounds from sulfuric acid leach solutions, McAndrew, et al. (11) consider up to 32 hydroxyl and sulfate complexing reactions and 13 precipitation reactions. Within a restricted pH range only a few of these equilibria are relevant and need to be considered. Nevertheless, equilibrium constants for the relevant reactions must be known. Furthermore, since most processes operate at elevated temperatures, it is essential that these parameters be known over a range of temperatures. The availability of this information is discussed below. 

We will now look at the relative amounts of ions in solution at the very end of the titration, i.e. after the end point has been reached and surpassed, and note that all of the chloride ion will have been consumed by the precipitation of solid AgCl, and that the addition offurther AgNO3 solution to the reaction solution merely dilutes it. At the end of the titration, we see that [C/ ] [Ag+]. 

Thus rate laws for precipitation reactions tend to be complicated, even in pure solutions. Mixed precipitates can be inhomogeneous solids with one component restricted to a thin outer layer because of slow diffusion. New solid phases can precipitate homogeneously onto the surfaces of existing solid phases. Weathering solids may provide host surfaces onto which more stable phases may precipitate. 

In the initial few weeks following submergence, the properties of the soil smface change markedly as a result of reductive dissolution and precipitation reactions. But in time, a steady- or quasi-steady-state is reached, and then the same rules govern the distributions of exchangeable ions between the soil solid and... 

---